This invention relates to a method for forming a synthetic turf game playing surface which closely simulates the feel and the playing characteristics of natural grass turf used for golf courses, tennis courts and other games played upon grass surfaces.
Synthetic turf game playing surfaces are formed of pile carpets whose piles or strands are fastened to a base or backing sheet. The piles or strands are typically formed of thin, flat, narrow strips of a suitable plastic material which may be gathered into tufts fastened to the base sheet. The base sheet may be a woven cloth, formed of suitable plastic material, with an adhesive type coating or binder applied to the base or backing to anchor the strands thereto. The particular construction of the pile carpet may vary considerably. In general, the carpet is made of a weather resistant or xe2x80x9coutdoorxe2x80x9d type of construction.
Such carpets are typically laid upon a prepared ground surface to form a game playing surface intended to simulate a natural grass playing field surface. For some game purposes, a resilient underpad may be placed beneath the carpet and upon a firm support surface to provide some shock absorbent effects. In addition, in some instances, sand or other particulate materials may be placed in a layer upon the upper surface of the carpet base sheet and around the strands. An example of this type of construction is shown in U.S. Pat. No. 4,389,435 issued Jun. 21, 1983 to Frederick T. Haas, Jr. Another example is shown in U.S. Pat. No. 4,637,942 issued Jan. 20, 1987 to Seymour A. Tomarin.
The synthetic plastic strips which form the blades, when made of an appropriate plastic, such as stretch oriented polypropylene extruded, thin and narrow strands, tend to shred longitudinally during use. That is, during the movements and forces of players upon the surfaces thereof, the ends of the strands tend to split into a plurality of slivers. These intertangle with each other and, where used, with the sand of a sand layer located on the carpet. An example of this effect is disclosed in U.S. Pat. No. 4,336,286 issued Jun. 22, 1982 to Seymour A. Tomarin.
An attempt to substantially increase the shredding or fraying of the synthetic blades to provide a dense, intertwined mat-like surface, by means of sandblasting the blades, is disclosed in U.S. Pat. No. 5,356,344 issued Oct. 18, 1994 and U.S. Pat. No. 5,373,667 issued Dec. 20, 1994, both to Alain Lemieux for a synthetic turf and a method of making a synthetic turf, respectively. In these patent disclosures, the grass-like synthetic blades are frayed by sandblasting the blades from above the carpet surface. Said blades may be made, for example, of polypropylene, nylon, polyester and the like, thin, narrow strips. Their upper, free ends are frayed or shredded by a blast of sand particles striking them. The frayed or shredded ends tend to intertwine or entangle to form a matted surface. However, the force of the sand blast, which is required to produce sufficient shredding, also tends to crush or permanently deform the blade strands downwardly against the base sheet of the carpet. This affects the desired uniformity, pliability and feel of the finished artificial turf surface.
Therefore, this present invention relates to an improvement to the method for shredding or fraying the artificial, plastic blade-like strands which avoids crushing, or permanently compressing or deforming or similarly damaging the blade strands by the sandblasting.
This invention contemplates shredding or fraying the upper end portions of the synthetic plastic blades into finely divided slivers, which entangle and intertwine with each other to form a dense, matted surface, by supporting the artificial turf carpet upon a resilient, cushioning underpad during the sandblasting step. Further, this invention contemplates, as an option, further separating the finely divided slivers of each strand from each other while entangling the slivers of adjacent strands better and more densely packing the mat formed from the intertwined slivers of adjacent strands, by spraying the strands with high pressure water, after the sandblasting step or by brushing the sandblasted surface or by both water spraying and brushing.
An object of this invention is to provide a densely matted surface upon the blade forming strands of the synthetic pile carpet by a sandblasting, or similar sand-like particulate blasting procedure, without crushing or permanently compressing the strands as a result of the procedure.
Another object of this invention is to provide a simple sandblasting type of procedure for shredding or fraying the upper ends of the pile strands of a synthetic turf carpet so as to form a densely matted playing surface comprising entangled or intertwined finely divided slivers formed on the ends of the strands and, in addition, maintaining the sand layer deposited upon the base sheet of the carpet by the covering mat.
Still another object of this invention is to provide a method for dividing into fine slivers the upper ends of the synthetic strands of a synthetic turf pile carpet rapidly, inexpensively, and without crushing, compressing or otherwise permanently compacting the otherwise upright blades formed by the strands.
These and other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a party.